Systems for timing glue guns in response to movement of workpieces such as carton blanks are known in the art. For example, U.S. Pat. No. 4,553,954, Sewell, et. al., for Automatic Case Erector and Sealer, Nov. 19, 1985 provides for control of a glue nozzle by means of electrical switches positioned to sense the carton as it is moved by the switch. Not only are electrical sensing switches critical in positioning and unreliable in operation because they mechanically break electrical current paths, but they are very limited in the ability to program a gluing system universally for any desired pattern of glue on a workpiece. Particularly when in an environment that has lint and dust from cartons in the vicinity, such switches can become contaminated. They are not always positionable where desired for control because of limitations of machine geometry. Thus, a more reliable and more universally programmable system is an objective of the present invention.
Glue rollers are also used to roll on glue as shown in U.S. Pat. No. 4,157,058, Vogel, for Long Seam Gluer, Jun. 5, 1979. These rollers give little flexibility of placement and programming for different seam lengths or cartons.
Computer controlled programmable gluing systems are very expensive, and require considerable expertise for set up and change from one gluing pattern to another. Thus, they cannot generally be operated by routine unexperienced labor usually hired for gluing cartons and the like in manufacturing plants. Even so, the programming procedure is long and tedious and can readily result in programming errors.
It is therefore an object of this invention to provide an inexpensive and simple to operate programmable general purpose gluing pattern control system that improves the state of the art.